Prostate cancer is a disease in which cancer develops in the prostate, a gland in the male reproductive system. Cancer occurs when cells of the prostate mutate and begin to multiply out of control. These cells may spread (metastasize) from the prostate to other parts of the body, especially the bones and lymph nodes. Prostate cancer may cause pain, difficulty in urinating, erectile dysfunction and other symptoms.
Rates of prostate cancer vary widely across the world. It is least common in South and East Asia, more common in Europe—though the rates vary widely between countries—and most common in the United States. According to the American Cancer Society, prostate cancer is least common among Asian men and most common among black men with figures for European men in between. However, these high rates may be affected by increasing rates of detection.
Prostate cancer develops most frequently in men over fifty. This cancer can only occur in men; the prostate is exclusively of the male reproductive tract. It is the second most common type of cancer in men in the United States, where it is responsible for more male deaths than any other cancer except lung cancer. However, many men who develop prostate cancer never have symptoms, undergo no therapy, and eventually die of other causes. Many factors, including genetics and diet, have been implicated in the development of prostate cancer.
Prostate cancer is most often discovered by physical examination or by screening blood tests, such as the PSA (prostate specific antigen) test. There is some current concern about the accuracy of the PSA test and its usefulness. Suspected prostate cancer is typically confirmed by removing a piece of the prostate (biopsy) and examining it under a microscope. Further tests, such as X-rays and bone scans, may be performed to determine whether prostate cancer has spread.
Prostate cancer is currently treated with surgery, radiation therapy, hormone therapy, occasionally chemotherapy, or some combination of these. The age and underlying health of the man as well as the extent of spread, appearance under the microscope, and response of the cancer to initial treatment are important in determining the outcome of the disease. Since prostate cancer is commonly a disease of older men, many will die of other causes before the prostate cancer can spread or cause symptoms. This makes treatment selection difficult. The decision whether or not to treat localized prostate cancer (a tumor that is contained within the prostate) with curative intent is a patient trade-off between the expected beneficial and harmful effects in terms of patient survival and quality of life.
Prostate cancer is typically diagnosed with a digital rectal exam and/or prostate specific antigen (PSA) screening. An elevated PSA level can indicate the presence of PCA. PSA is used as a marker for prostate cancer because it is essentially restricted to prostate cells. A healthy prostate will produce a stable amount—typically below 4 nanograms per milliliter, or a PSA reading of “4” or less—whereas cancer cells produce escalating amounts that correspond with the severity of the cancer. A level between 4 and 10 may raise a doctor's suspicion that a patient has prostate cancer, but PSA values within this range are just as likely the result of aging-associated increases in prostate volume due to benign prostatic hypertrophy (BPH) and/or prostate cancer. Serum PSA values above 10 are more reliably diagnostic of prostate cancer, and values above 50 may show that the tumor has spread elsewhere (e.g., metastasized) in the body.
The development of additional serum and tissue biomarkers specific to cancer (e.g., prostate) are needed to supplement currently available screening methods. In particular, additional serum and tissue biomarkers that might distinguish between benign prostatic hypertophy and prostate cancer among men with low (≦10 ng/ml) serum PSA would be useful for determining which patients are at higher risk for prostate cancer and require diagnostic needle biopsy from those patients at low risk who might benefit from a watchful waiting approach. In addition, new therapeutic treatments (e.g., targeted at newly identified biomarkers) are needed for the treatment of cancer (e.g., prostate cancer) and are of broad interest to the medical community, as well as to the pharmaceutical and biotech industries. The present invention addresses these issues.